The present invention relates to a method of detaching an article fixed through a pressure sensitive adhesive double coated sheet and a detachment apparatus.
For example, a semiconductor wafer such as silicon is produced in the form of a disc of large diameter. A circuit pattern is formed on a surface of the semiconductor wafer, and the back thereof is ground.
In recent years, there is a demand for the reduction of the thickness of semiconductor chips for IC cards and the like. It is necessary to reduce the thickness of semiconductor chips produced from the semiconductor wafer, which has conventionally been 300-400 xcexcm, to about 100-50 xcexcm. In this case, a pressure sensitive adhesive sheet, which is used for fixing the semiconductor wafer to a table and the like while protecting the surface of the semiconductor wafer furnished with a circuit pattern, is produced by coating a soft base material with a pressure sensitive adhesive.
It is extremely difficult to grind the semiconductor wafer to a thickness as small as about 50 xcexcm with the use of such a soft pressure sensitive adhesive sheet. When the conventional pressure sensitive adhesive sheet is stuck to the wafer, it has been experienced that the tension applied at the time of sticking is accumulated as a residual stress. As a result, in the event that the diameter of the wafer is large or grinding to an extremely small thickness is intended, the residual stress of the pressure sensitive adhesive sheet is greater than the strength of the wafer. Therefore, a force for canceling the residual stress is brought about to cause the wafer to suffer from a warpage. Moreover, it has been experienced that, in the use of the soft base material, the wafer is broken during the transportation because the wafer is brittle after the grinding.
Also, it is practiced to fix the semiconductor wafer to a support plate such as a glass plate, a quartz plate or an acrylic plate with the use of a wax in place of the pressure sensitive adhesive sheet comprising a soft base and to thereafter effect grinding thereof. In this method, it is difficult to apply the wax at a uniform thickness. Moreover, after the completion of the grinding, the wax must be washed away with, for example, an organic solvent, the washing being time-consuming work. Further, thereafter in the event of dicing into small squares, it is required to stick a dicing tape to the wafer having been freed of the wax, this sticking causing an additional workload. Therefore, the use of the wax is not suitable to the processing of electronic components by an automatic line. Moreover, in the sticking of the semiconductor wafer to a support plate such as a glass plate with the use of a wax as well, it is difficult to detach them from each other at a later stage, so that breakage cannot be avoided.
In these circumstances, the applicant has proposed a pressure sensitive adhesive double coated sheet which fixes the wafer to a support plate in place of the wax and which can easily be detached from the wafer.
The present invention provides a method of detaching an article fixed through a pressure sensitive adhesive double coated sheet and a detachment apparatus therefor, which, by virtue of the use of the above pressure sensitive adhesive double coated sheet, realize effective detachment of articles and ensure suitability to processing by an automatic line.
The method of detaching an article fixed through a pressure sensitive adhesive double coated sheet according to the present invention comprises the steps of:
holding a laminate unit, between a pair of sandwiching means, the sandwiching means so arranged as to enable interposition of the laminate unit, said laminate unit being obtained by fixing an article to a support plate through a pressure sensitive adhesive double coated sheet capable of being deformed by heating to thereby exert a detachment effect;
heating the laminate unit by heating means so that the pressure sensitive adhesive double coated sheet is deformed to thereby reduce an area of contact between the pressure sensitive adhesive double coated sheet and the article, with the result that the article is apart from the pressure sensitive adhesive double coated sheet.
In this method, the pressure sensitive adhesive double coated sheet is deformed by heating, so that the pressure sensitive adhesive double coated sheet stuck to the article can be detached easily from the article.
Preferably, the pair of sandwiching means comprises a first table and a second table.
The detaching method of the present invention is preferably characterized in that the pair of sandwiching means are held so as to enable providing therebetween such a clearance that the deformation of the pressure sensitive adhesive double coated sheet is not prevented by the sandwiching means.
In this case, the pressure sensitive adhesive double coated sheet is shrunk, and, when the pressure sensitive adhesive double coated sheet is curved in the direction of the thickness thereof, the article can easily be detached from the pressure sensitive adhesive double coated sheet.
Further, in the present invention, it is preferred that the pressure sensitive adhesive of at least one side of the pressure sensitive adhesive double coated sheet is composed of an ultraviolet curable pressure sensitive adhesive, with the support plate permeable for ultraviolet rays, and that, prior to holding the laminate unit between the sandwiching means, the pressure sensitive adhesive double coated sheet is irradiated with ultraviolet rays having been passed through the support plate, so that the ultraviolet curable pressure sensitive adhesive has its adhesive strength reduced.
In the employment of this construction, the adhesive strength is reduced prior to the deformation of the pressure sensitive adhesive double coated sheet, so that the deformation can be easily accomplished.
In another aspect of the present invention, there is provided a detachment apparatus for detaching an article (article) fixed through a pressure sensitive adhesive double coated sheet, intended to detach an article fixed to a support plate through a pressure sensitive adhesive double coated sheet capable of being deformed by heating to thereby exert a detachment effect, comprising:
a pair of sandwiching means arranged so as to enable interposition therebetween, and
heating means for deforming the pressure sensitive adhesive double coated sheet.
Preferably, the pair of sandwiching means comprises a first table capable of fixing the support plate side by suction and a second table capable of fixing the article side by suction.
It is also preferred that the pair of sandwiching means are held so as to enable providing therebetween such a clearance that the deformation of the pressure sensitive adhesive double coated sheet is not blocked by the sandwiching means.
The detachment apparatus preferably further comprises an ultraviolet irradiation device capable of irradiating the pressure sensitive adhesive double coated sheet with ultraviolet rays so that the pressure sensitive adhesive double coated sheet has its adhesive strength reduced.
Moreover, the detachment apparatus preferably further comprises means for removing residues of the pressure sensitive adhesive double coated sheet.
With the use of the above detachment apparatus of the present invention, the pressure sensitive adhesive double coated sheet is deformed by heating so that the deformed pressure sensitive adhesive double coated sheet can be detached with enhanced reliability without damaging the article.